package com.ciko.code.utils;

import java.io.UnsupportedEncodingException;


/**
 * Base64工具类
 * @author yangwc
 *
 */
public class Base64 {

    private static final byte[] encodingTable = { (byte) 'A', (byte) 'B',
            (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
            (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L',
            (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q',
            (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V',
            (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a',
            (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
            (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k',
            (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
            (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
            (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
            (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4',
            (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
            (byte) '+', (byte) '/' };

    /**
     * encode the input data producong a base 64 encoded byte array.
     *
     * @return a byte array containing the base 64 encoded data.
     */
    public static byte[] encode(byte[] data) {
        byte[] bytes;

        int modulus = data.length % 3;
        if (modulus == 0) {
            bytes = new byte[4 * data.length / 3];
        } else {
            bytes = new byte[4 * ((data.length / 3) + 1)];
        }

        int dataLength = (data.length - modulus);
        int a1, a2, a3;
        for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
            a1 = data[i] & 0xff;
            a2 = data[i + 1] & 0xff;
            a3 = data[i + 2] & 0xff;

            bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
            bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
            bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
            bytes[j + 3] = encodingTable[a3 & 0x3f];
        }

		/*
		 * process the tail end.
		 */
        int b1, b2, b3;
        int d1, d2;

        switch (modulus) {
            case 0: /* nothing left to do */
                break;
            case 1:
                d1 = data[data.length - 1] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = (d1 << 4) & 0x3f;

                bytes[bytes.length - 4] = encodingTable[b1];
                bytes[bytes.length - 3] = encodingTable[b2];
                bytes[bytes.length - 2] = (byte) '=';
                bytes[bytes.length - 1] = (byte) '=';
                break;
            case 2:
                d1 = data[data.length - 2] & 0xff;
                d2 = data[data.length - 1] & 0xff;

                b1 = (d1 >>> 2) & 0x3f;
                b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
                b3 = (d2 << 2) & 0x3f;

                bytes[bytes.length - 4] = encodingTable[b1];
                bytes[bytes.length - 3] = encodingTable[b2];
                bytes[bytes.length - 2] = encodingTable[b3];
                bytes[bytes.length - 1] = (byte) '=';
                break;
        }

        return bytes;
    }

    public static String encode(String data,String charset) {
        try {
            return new String(encode(data.getBytes(charset)));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
            return null;
        }
    }

    /*
     * set up the decoding table.
     */
    private static final byte[] decodingTable;

    static {
        decodingTable = new byte[128];

        for (int i = 0; i < 128; i++) {
            decodingTable[i] = (byte) -1;
        }

        for (int i = 'A'; i <= 'Z'; i++) {
            decodingTable[i] = (byte) (i - 'A');
        }

        for (int i = 'a'; i <= 'z'; i++) {
            decodingTable[i] = (byte) (i - 'a' + 26);
        }

        for (int i = '0'; i <= '9'; i++) {
            decodingTable[i] = (byte) (i - '0' + 52);
        }

        decodingTable['+'] = 62;
        decodingTable['/'] = 63;
    }

    /**
     * decode the base 64 encoded input data.
     *
     * @return a byte array representing the decoded data.
     */
    public static byte[] decode(byte[] data) {

        byte[] bytes;
        byte b1, b2, b3, b4;

        data = discardNonBase64Bytes(data);

        if (data[data.length - 2] == '=') {
            bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
        } else if (data[data.length - 1] == '=') {
            bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
        } else {
            bytes = new byte[((data.length / 4) * 3)];
        }

        for (int i = 0, j = 0; i < data.length - 4; i += 4, j += 3) {
            b1 = decodingTable[data[i]];
            b2 = decodingTable[data[i + 1]];
            b3 = decodingTable[data[i + 2]];
            b4 = decodingTable[data[i + 3]];

            bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[j + 2] = (byte) ((b3 << 6) | b4);
        }

        if (data[data.length - 2] == '=') {
            b1 = decodingTable[data[data.length - 4]];
            b2 = decodingTable[data[data.length - 3]];

            bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
        } else if (data[data.length - 1] == '=') {
            b1 = decodingTable[data[data.length - 4]];
            b2 = decodingTable[data[data.length - 3]];
            b3 = decodingTable[data[data.length - 2]];

            bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
        } else {
            b1 = decodingTable[data[data.length - 4]];
            b2 = decodingTable[data[data.length - 3]];
            b3 = decodingTable[data[data.length - 2]];
            b4 = decodingTable[data[data.length - 1]];

            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }

        return bytes;
    }

    /**
     * decode the base 64 encoded String data.
     *
     * TODO: Use the byte version to avoid duplication?
     *
     * @return a byte array representing the decoded data.
     */
    public static byte[] decode(String data) {
        byte[] bytes;
        byte b1, b2, b3, b4;

        data = discardNonBase64Chars(data);

        if (data.charAt(data.length() - 2) == '=') {
            bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
        } else if (data.charAt(data.length() - 1) == '=') {
            bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
        } else {
            bytes = new byte[((data.length() / 4) * 3)];
        }

        for (int i = 0, j = 0; i < data.length() - 4; i += 4, j += 3) {
            b1 = decodingTable[data.charAt(i)];
            b2 = decodingTable[data.charAt(i + 1)];
            b3 = decodingTable[data.charAt(i + 2)];
            b4 = decodingTable[data.charAt(i + 3)];

            bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[j + 2] = (byte) ((b3 << 6) | b4);
        }

        if (data.charAt(data.length() - 2) == '=') {
            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];

            bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
        } else if (data.charAt(data.length() - 1) == '=') {
            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];
            b3 = decodingTable[data.charAt(data.length() - 2)];

            bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
        } else {
            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];
            b3 = decodingTable[data.charAt(data.length() - 2)];
            b4 = decodingTable[data.charAt(data.length() - 1)];

            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }

        return bytes;
    }

    /**
     * Decode the string and convert back the decoded value into a string using
     * the specified charset. Use default encoding if charset is null or
     * invalid.
     */
    public static String decode(String data, String charset) {
        if(data == null){
            return null;
        }

        if(data.length() <= 0){
            return "";
        }

        if (charset == null) {
            // use default
            return new String(decode(data));
        }

        try {
            return new String(decode(data), charset);

        } catch (UnsupportedEncodingException ex) {
            return new String(decode(data));
        }
    }

    /**
     * Decode the string and convert back the decoded value into a string using
     * the specified charset. Use default encoding if charset is null or
     * invalid.
     */
    public static String decode(byte[] data, String charset) {
        if (charset == null) {
            // use default
            return new String(decode(data));
        }

        try {
            return new String(decode(data), charset);

        } catch (UnsupportedEncodingException ex) {
            return new String(decode(data));
        }
    }

    // --------------------------------------------------------- Private Methods

    /**
     * Discards any characters outside of the base64 alphabet (see page 25 of
     * RFC 2045) "Any characters outside of the base64 alphabet are to be
     * ignored in base64 encoded data."
     *
     * @param data
     *            the base64 encoded data
     * @return the data, less non-base64 characters.
     */
    private static byte[] discardNonBase64Bytes(byte[] data) {
        byte temp[] = new byte[data.length];
        int bytesCopied = 0;

        for (int i = 0; i < data.length; i++) {
            if (isValidBase64Byte(data[i])) {
                temp[bytesCopied++] = data[i];
            }
        }

        byte newData[] = new byte[bytesCopied];

        System.arraycopy(temp, 0, newData, 0, bytesCopied);

        return newData;
    }

    /**
     * Discards any characters outside of the base64 alphabet (see page 25 of
     * RFC 2045) "Any characters outside of the base64 alphabet are to be
     * ignored in base64 encoded data."
     *
     * @param data
     *            the base64 encoded data
     * @return the data, less non-base64 characters.
     */
    private static String discardNonBase64Chars(String data) {

        StringBuffer sb = new StringBuffer();

        int length = data.length();

        for (int i = 0; i < length; i++) {
            if (isValidBase64Byte((byte) (data.charAt(i)))) {
                sb.append(data.charAt(i));
            }
        }

        return sb.toString();
    }

    /**
     * Checks is the given byte is in base64 alphabet
     *
     * @param b
     *            the byte to check
     * @return boolean true if the byte is in base64 alphabet
     */
    private static boolean isValidBase64Byte(byte b) {
        if (b == '=') {
            return true;
        } else if (b < 0 || b >= 128) {
            return false;
        } else if (decodingTable[b] == -1) {
            return false;
        }
        return true;
    }

    /**
     *
     * @Title: base64Encode
     * @Description: DES加密
     * @param data
     * @param key
     * @param charSet
     * @return
     * @return String 返回类型
     * @throws
     */
    public final static String base64Encode(String data, String key, String charSet) {
        try
        {
            return encode(DESUtil.encrypt(data, key), charSet);
        }
        catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }
}

